The present invention pertains to the field of control systems for land vehicles, in particular for wheeled motor vehicles.
In a conventional manner, motor vehicles are provided with a chassis, a cabin, wheels connected to the chassis by a suspension mechanism with steered front wheels controlled by a steering wheel at the disposal of the driver in the cabin of the vehicle.
The document FR-A-2 681 303 describes a rear steering control device for motor vehicle with four steered wheels, comprising a cam-forming plate and two idlers disposed in one and the same vertical mid-plane containing the longitudinal axis of a rear steering bar controlling the swiveling of the rear wheels.
This document also describes that, in order to obtain the best possible road behavior of the vehicle, it is necessary to deflect the rear wheels in the same direction as the front wheels for a value of steering wheel deflection angle below a predetermined threshold value and in the opposite direction to the front wheels when the value of the deflection angle exceeds the threshold value. A desirable vehicle “oversteer” effect would thus be obtained when the angle of deflection is relatively large, for example when the vehicle is being parked in a garage or a parking lot, and a likewise desirable “understeer” effect would be obtained when the angle of deflection is relatively small as is the case when the vehicle is running relatively fast.
Nevertheless, such a device, which is relatively crude, does not make it possible to act finely on the behavior of the vehicle.
Patent application FR-A-2 864 001 (Renault) is aimed at a method and a system for controlling steered rear wheel deflection intended for a vehicle. As a function of the front wheel deflection angle, of vehicle movement data, and of an anterior rear wheel deflection setpoint, a current rear wheel deflection setpoint is formulated. This method is satisfactory and makes it possible to reduce the risks of loss of control, which may be due to a vehicle response which is unsuitable as a result of being too lively, insufficiently damped or else quite unpredictable.
The Applicant has realized that it was desirable to further increase operating safety and to monitor the rear wheel deflection setpoint, aberrant values of which may be due to defective components, for example a corrupted memory area or flawed setup of an algorithm. Complete redundancy of the hardware and software components would have offered a solution which turns out to be much too expensive and cumbersome.